BRPI0606850A2 - conveyor roller for high temperature applications, process for assembling a conveyor roller and use of a conveyor roller - Google Patents

Abstract

CARRIER ROLLER FOR HIGH TEMPERATURE APPLICATIONS, PROCESS FOR ASSEMBLING A CARRIER ROLLER AND USING A CARRIER ROLLER. The present invention relates to conveyor rollers used in high temperature applications, and more particularly relates to an improved end cap assembly for such rollers. According to the invention, the conveyor roller (1) comprises a) a ceramic spool (2), b) at each end (21, 22) of the ceramic spool (2), an end cap (4) comprising a metal ferrule (41) and having a certain internal circumference adapted to fit over one end (21) of the ceramic spool; and c) interposed between each end (21, 22) of the ceramic spool (2) and the end cap (4) is a resilient metal tolerance ring (3) having a plurality of circumferentially arranged corrugations. This conveyor roller can withstand temporary overheating or blocking without damage.

Description

"CARRIER ROLLER FOR HIGH TEMPERATURE APPLICATIONS, PROCESS FOR ASSEMBLING A CARRIER ROLLER AND USING A CARRIER ROLLER" Description.

The present invention relates to used conveyor rollers.

in high temperature applications, and more particularly concerns an improved end cap assembly for such rollers.

A conveyor roller used in high temperature applications may comprise a ceramic reel having metal end caps.

Typically, the ceramic spool comprises fused silica. End caps allow easy mounting on a bearing or drive wheel. For example, in tempering glass applications, the ceramic reel supports glass sheet, and end caps allow mechanical coupling with the drive mechanism. The end caps should securely adhere to the reel to allow the reel to rotate at the desired speed. Eccentric rotation is generally undesirable as this would create an uneven support surface for the glass sheet.

The different thermal expansions of the ceramic reel and metal end caps make it difficult to securely attach the end caps to the reel and can create eccentric rotations. Several methods have been proposed to overcome this difficulty. US Patent No. 3,867,748 teaches attaching end caps to a trailer using an adhesive. US Patent No. 4,242,782 proposes to fix end caps using rubber O-rings. Adhesives and O-rings may become bendable and lose holdability at elevated temperatures, causing eccentric rotation of the reel and slippage between the end caps and the reel. If, by accident, the adhesive and O-ring have been subjected to such high temperatures, they definitely lose their holding capacity so that even when the temperature returns to its normal value, slip is still observed. For this reason, the attachment of end caps on a reel using adhesive or O-ring is limited to low temperature applications (below 250 ° C).

Metal connectors have also been used to secure an end cap to a reel. US Patent No. 5,316,129 or US Patent No. 4,404,011 describes the use of a helically wound coil between the carriage and the end cap. The coil includes curved portions and straight portions that allow continuous contact between the end cap and the reel regardless of different coefficients of thermal expansion. The spring coil

The flat side of this document consists of a succession of relatively long portions that are relatively thin. Under these conditions, a significant flexibility of the coil elements is observed. Consequently, to obtain sufficient torque to hold the end cap on the reel, it is necessary to pre-tension the coil

significantly. If the temperature accidentally rises (temporary overheating), the torque and consequently the fastening of the end cap to the reel is required. Also, when the system cools, the torque is not recovered. Pats. US Nos. 5,906,567 and 5,370,596 describe curved bimetallic shims for securing the end cap to the

I reeled. The curvature of the bimetallic shims changes with temperature, thus maintaining a secure fixation between the carriage and the end cap. Mounting and repairing a coil spring or bimetallic system can, however, be difficult. In addition, such metal connectors are particularly suited for specific temperature ranges (usually 400 ° C and above).

high). Outside this range, eccentric rotation can be observed.

Mechanical fasteners can be used to attach an end cap to a reel. US Patent No. 4,751,776 shows an end cap having an annular distribution of screws that are threaded into a ferrule at the end of a carriage. The bolts are tightened to secure the end cap to the reel, but thermal expansion and contraction can loosen the bolts causing eccentric rotation and slipping. In this case, the screws will seriously damage the surface of the reel. Screws have also been keyed to a flat surface machined over the carriage face to ensure coaxial rotation. Mounting and repairing such gloves and locking key is time consuming. FR 2,550,172 describes an end cap including a metal collar between the carriage and the end cap. The end cap is locked in place with a key fitted to a flat surface of the carriage. The collar has a higher thermal expansion than the end cap, and is intended to compensate for the difference in thermal expansion between the end cap and the reel. US Patent No. 5,146,675 discloses a screw that can be detached to force a metal plate against a flat portion on the carriage, which presses the carriage against the inner surface of the end cap. The end cap includes an access opening which allows the screw, metal plate and end cap to be welded together, thereby preventing the screw from popping out. Effectively, the end cap and reel connect via a single geometry axis, that is, the screw. Thermal cycling through a single contact geometry can cause eccentric rotation and movement of the metal plate relative to the carriage. Such movement may even cause the plate to contact the edge of the flat portion and break the reel.

Another problem that is often observed with prior art conveyor rollers is that of locking. For example, in the event that the transported article is blocked or in the case of mechanical gripping, the drive mechanism will continue to operate and will transmit a twisting motion to the end cap. Under these conditions, either the ceramic reel or fixing means will break. The same consequences are observed in the long run when the conveyor roller is subjected to brutal acceleration or deceleration.

The need persists for an end cap that is fixed and centrally secured to a ceramic reel within a wide range of application temperatures. The end cap must be able to withstand temporary overheating and regain its holding capacity when the temperature is returned to normal without causing eccentric rotation. The end cap should also be easy to install. The conveyor roller must also be able to withstand temporary line locking or gripping as well as brutal acceleration or deceleration.

These objectives and others are achieved with a conveyor roller according to claim 1. More specifically, the tolerance ring interposed between the end cap and the end of the ceramic reel (also called the roller neck) will fixedly secure the reel to the cap. very efficient torque transfer and prevent eccentric rotation of the reel. In addition, in the event of temporary overheating, the end cap and tolerance ring will thermally expand while the dimensions of the ceramic reel will not significantly change. In this way, the holding capacity of the tolerance ring will decrease and the reel will begin to slide into the end cap. When the temperature will return back to normal, the end cap and tolerance ring will return to their "normal" dimensions and the holding capacity will be fully restored. It is important to note that during this temporary overheating, the reel will remain coaxial with the end cap thanks to the tolerance ring.

Tolerance rings are known from US Patent No. 3,061,386. They are described as made from resilient metal and have a plurality of circumferentially arranged corrugations of defined height and pitch, with both the height and pitch of the corrugations significantly smaller than the diameter of the ring. Typically, the pitch is smaller than 10% in diameter and preferably less than 8% in diameter. Typically, the height is less than 5% in diameter and preferably less than 3% in diameter. US Patent No. 3,142,887 indicates a method of producing such tolerance rings. This design is very particular and may be opposed to a helically wound flat-sided coil. Due to this particular design, the tolerance ring shows very significant flexibility. Numerous variants of tolerance rings have been described in the art (variable heights, steps, multiple rows of aligned or offset corrugations, ...) and are sold through various companies. In principle, all these types of tolerance rings can be used. It is preferable to have an open tolerance ring having a length less than the inner circumference of the end cap, as when the roll neck is introduced into the end cap provided with the tolerance ring, it must be able to accommodate the slight dimensional variations that could occur during the manufacture of the reel or end cap. It could be advantageous to have a second tolerance ring open parallel to the first ring but with its opening displaced so as to improve the coaxiality of the reel in the end cap. It is also very advantageous to have a relatively limited pitch (less than 20 mm between two wave "heights") to achieve high stiffness.

It is preferred to have the corrugation (s) oriented inwards so that in the event of slippage this will occur only with respect to the "tolerance ring - terminal buffer" pair and will not damage the surface of the I reeled.

According to one embodiment of the invention, at least one of the tolerance rings is provided with at least one tab, while in parallel the corresponding end of the ceramic reel is provided with one or more adapted notches (). to receive the tolerance ring tabs. Such an arrangement will prevent relative movement in an axial direction between the tolerance ring and the reel. Since it is preferable to prevent removal of the reel from the tolerance ring especially during temporary overheating (ie when the pressure exerted on the reel via the tolerance ring is minimal), it is preferable to have the tab (s) oriented so that the end of the tab will cooperate with the notch wall closest to the end of the reel. In this way the reel can only move slightly towards its end and abut the bottom of the end cap. If such tolerance rings provided with these advantageous flaps are provided on both sides of the carriage, all relative movements of the carriage are prevented.

According to another embodiment, the tolerance ring is provided with at least two tabs and one tab has an orientation opposite to at least one other tab. In this way all relative movements of the reel with respect to a single tolerance ring are prevented.

As indicated above, the end cap has an inner circumference for receiving a tolerance ring and one end of a reel. Advantageously, the end cap is provided with a step to limit relative movements between the tolerance ring and the end cap. According to a particularly preferred embodiment, the end cap is provided with a slot adapted to receive the tolerance ring. In this way all axial movements of the tolerance ring with respect to the end cap are prevented even in the event of temporary overheating. It is especially advantageous to combine the presence of tabs on the tolerance ring with the slot in the end cap to prevent any relative movement of the reel with respect to the end cap during temporary overheating.

According to a particular embodiment of the invention, both the end cap and the ceramic reel receive a mark once when assembled together. Both marks are in alignment with each other so that if a temporary overheating has occurred and torque has ceased to be transmitted to the reel, the operator will observe this phenomenon only by noting that the marks are shifted. He could then take appropriate action.

The present invention also relates to a process for mounting a conveyor roller as described above. This process comprises the steps of adjusting a tolerance ring on the ferrule of an end cap and forcing each end of the ceramic reel into the end cap. The order of the steps is important otherwise, the position of the tolerance ring with respect to the reel may change during its insertion into the end cap. Generally, the end of the ceramic reel is forced into the end cap provided with the tolerance ring with a hydraulic press exerting a pressure of several hundred kg / cm2, for example 1000 kg / cm2.

In the case where the tolerance ring is provided with one or more tab (s), the process comprises another step of flexing these tab (s) inwards and aligning the reel so that the tab (s) fit with the corresponding reel notch (s).

The conveyor roller according to the invention may be used to transport a sheet or sheet of metal (e.g. glass or metal) for any type of heat treatment of the sheet or sheet of metal or a coating applied thereon. This conveyor roller is particularly suitable for transporting flat articles in an environment subject to significant temperature variations.

To further explain the invention, an exemplary non-limiting method of implementation is described below with reference to the accompanying drawings, in which:

Figures 1, 2 and 3 are schematic sectional views of roller conveyors according to one embodiment of the invention; and

Figure 4 shows a graph of transmitted torque (Nm) versus temperature (° C).

In these figures, 1 generally represents a conveyor roller "comprising a ceramic reel 2 having two ends 21 and 22. An end cap 4 comprising a ferrule 41 is disposed at both ends of the reel 2 (only the end cap provided at end 21 is shown in Figure 1). A tolerance ring 3 is inserted into the end cap 4. The end cap 4 has a regular inner surface in figure 1, while figures 2 and 3 respectively show an end cap 4 provided with a step 42 or a slot 43 to restrict the movements of tolerance ring 3 in the end cap.

The tolerance ring may be provided with a tab 31 cooperating with the wall of a notch provided at the end of the ceramic reel 21. In Figures 1 to 3, the tab 31 cooperates with the notch wall closest to the end 21 of the cart 2.

Experiments were performed with a conveyor roller according to FIG. 2 to demonstrate the possibility that the conveyor roller could withstand temporary overheating and recover its normal operating conditions when the temperature returns to normal.

An open tolerance ring 3 with inwardly oriented corrugations (length: 242 mm; width: 25 mm; height: 1.9 mm; pitch: 9.4; stainless steel) is inserted into an end cap 4 (carbon steel ) having an internal diameter of 80 mm. The operation is repeated for the second terminal buffer. Both ends of a reel 21 and 22 (77 mm diameter) are forced into the end plugs 4. Such a conveyor roller is intended to work at temperatures between room temperature and 200 ° C. The person skilled in the art will easily find through routine experiments different disposition (different metals operating at different temperatures).

Figure 4 shows the transmitted torque (Nm) against temperature (° C). It can be seen that the torque decreases progressively to 5 around 300 ° C where its value is less than 50 Nm and the reel begins to slide. When the temperature returns back to normal (lower curve), the transmitted torque increases rapidly to recover its original value. From 300 ° C, the reel stops sliding. After disassembly of the conveyor roller, it was observed that both ends of the ceramic reel were in perfect condition and were not damaged mainly during temporary overheating. Figure 4 also shows (dotted lines) the transmitted torque (Nm) against temperature (° C) for a system as described in US Patent 5,316,129. Such a system is made up of relatively long and flat elements. When the system is subjected to heat, the transmitted torque decreases progressively (curve A) to around 300 ° C where the elastic limit of the system is reached. At this point, the transmitted torque drops dramatically and the roller begins to slide into the end cap. When the system returns back to normal (curve B), the system does not fully recover the original torque once the system elastic limit has been exceeded. When again subjected to heat and cooling (C and D curves), the same phenomenon is observed, with the consequence that after only a few heating / cooling cycles, the torque is no longer transmitted so that the conveyor roller has to be replaced. Such conveyor rollers are clearly not suitable for use in an environment suitable for significant temperature variations. In contrast, the conveyor roller of the invention has proved to be fully satisfactory for such a use requirement.

Claims (12)

Conveyor roller (1) for high temperature applications, characterized in that it comprises: (a) a ceramic reel (2), (b) at each end (21,22) of the ceramic reel (2), a terminal plug ( 4) comprising a metal ferrule (41) and having a certain internal circumference adapted to fit over one end (21) of the ceramic carriage; and c) interposed between each end (21, 22) of the ceramic carriage (2) and the end cap (4), a resilient metal tolerance ring (3) having a plurality of circumferentially arranged corrugations. Conveyor roller according to claim 1, characterized in that the tolerance ring has a pitch of less than 20 mm. Conveyor roller according to claim 1 or 2, characterized in that the tolerance ring (3) is open and is shorter than the inner circumference of the end cap (4). Conveyor roller according to any one of claims 1 to 3, characterized in that the corrugations of the tolerance ring (24) extend inwardly. Conveyor roller according to claim 3 or 4; characterized in that a plurality of open tolerance rings (3) are interposed between each end (21, 22) of the ceramic carriage (2) and the end cap (4) and wherein the openings of the tolerance rings are displaced. Conveyor roller (1) according to any one of claims 1 to 5, characterized in that at least one of the tolerance rings (3) is provided with at least one flap (31) and where the corresponding end (21) is provided. The ceramic carriage (2) is provided with notches (211) adapted to receive the tabs (31) of the tolerance ring (3). Conveyor roller according to claim 6, characterized in that the flap (31) is oriented so that the flap end will cooperate with the notch wall (211). ) closest to the end (21) of the reel (2). Conveyor roller according to claim 7, characterized in that the tolerance ring is provided with at least two tabs and at least one tab has an orientation opposite to at least one other tab. Conveyor roller according to any one of claims 1 to 8, characterized in that the end cap is provided with a step (42) or a slot adapted to receive the tolerance ring (3). Method for mounting a conveyor roller according to any one of claims 1 to 9, characterized in that it comprises the steps of: a) adjusting a tolerance ring on the ferrule of a terminal plug; ceramic reel into the end cap. A method according to claim 10, characterized in that it comprises another step a ') of flexing one or more inward tolerance ring tab (s) and a step b') of aligning the reel so as to that the tab (s) fit with the corresponding reel notch (s). Use of a conveyor roller (1) according to any one of claims 1 to 9, characterized in that it is for transporting flat articles in an environment subject to significant temperature variations.